As a result of secondary recovery requirements in oil fields, hot, often saline and corrosive water containing a variety of impurities is pumped at high pressures into the ground to force the oil out. Although the pipes used in this process usually have interior protective plastic linings, the areas where the pipe sections have been welded together do not have such a lining and are subject to very high corrosion rates. In order to prevent corrosion in these weld areas, an internal pipe corrosion protection device has been developed.
The instant invention is a device which is placed in general position inside the pipe prior to the joining of two pipe sections and which, when located directly beneath the welded and internally exposed joint after the joint has been welded, is expanded by application of external heat which causes the unique shape memory metal delivery means to expand radially so as to apply a corrosion-resistant liner means and heat activated bonding means to the inside of the pipe joint. The unique structure and configuration of the delivery means applies the liner means and the flowable bonding means progressively into intimate contact with the inside of the pipe wall to thereby prevent the formation of voids in said bonding means.
In the past, memory metals have been utilized in mechanical composite pipe couplings to force tensile load bearing members into gripping contact with pipes and tubing. Commonly assigned Australian Patent Number 74153/74 to C. L. Martin discloses the use of such memory metal for drivers to be utilized externally and internally with respect to pipes to be joined to simultaneously force tensile load bearing members of various configurations into the exterior or interior surface of the pipes. Likewise, commonly assigned British Patent Number 1,554,431 to C. L. Martin discloses the use of various configurations of memory metal alloy to secure patch members over ruptured pipe sections. These configurations may include the use of a polymeric coating for a gas tight seal. Commonly assigned U.S. Pat. No. 4,197,880, to J. M. Cordia discloses a compressed, axially slit, cylindrical memory metal driver member which is held in a radially compressed configuration by a thermoplastic retainer means, and is used to drive a foamable material toward the inside wall of a pipe.
None of the above described references suggest means to bond a chemically resistant liner to the inside of a pipe, especially in the area of a weld which is irregular in surface condition. The instant invention is unique in providing a highly expansible delivery means which progressively radially enlarges so as to apply a liner means and a flowable bonding means to smooth or irregular surfaces to preclude air entrapment, i.e. void areas, between said liner means and the inside of the pipe. Aside from the potential severe corrosion problems associated with any void areas, a major problem is encountered when a protectively lined pipe is pressurized and then later de-pressurized. Over time, any void in a pressurized pipe may become pressurized by the components in fluid in the pipe. When the pressure in the pipe is rapidly reduced the void can in essence explode, thereby damaging the integrity of the corrosion resistant liner. The configuration and articulation of the delivery means of the instant invention inherently causes a "pumping" wave of the bonding means, thereby bonding a chemically resistant liner means to the joint interior surface in a manner free of voids.